> I want to use a modulation technique because the data is going to be
> multiplexed with a power rail.  I expect the power rail to be pretty
> noisy, as it will have feeds to brushed DC motors.  AFAIK, AM is
> susceptible to noise generated arcing, and FM is less so.  That is why I
> wanted to use FM.

As you have already stated that this is for model railway application, why 
not just go with the proposed NMRA standard? 

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